1. Field of the Invention
The present invention relates to a soap-free, non-lathering shave lotion, and more particularly, to an improved soap-free, non-lathering shave lotion that increases surface adherence. This invention also relates to methods for shaving using this improved formulation, and a method for increasing the surface adherence ability of a soap-free, non-lathering shave lotion.
2. Related Art
Shaving preparations have long been available as powders, creams, and foams formulated to exhibit excellent lathering ability. More recently, consumers have been introduced to gel shaving compositions, which can be worked into a lather when rubbed against the skin.
Shaving preparations generally include soap as a major component. As used herein, "soap" means a salt of a fatty acid with a base. Examples are the salts of fatty acids with ammonia, low molecular weight amines (especially alkanolamines), and alkali metals (especially sodium and potassium). Other fatty acid salts result from the reaction of metallic cations (e.g., zinc, aluminum, and alkaline earth metals such as calcium and magnesium) with long chain fatty amines. The most common soaps used in shaving preparations are stearates and palmitates.
A drawback to using soap, however, lies in its tendency to cause irritation to the skin, particularly to delicate and broken skin, during shaving. Soap-containing shaving preparations can also cause drying of the skin and premature dulling of razor blades.
Accordingly, in recent years, the cosmetics industry has developed soap-free, non-lathering shaving preparations, as discussed, for example, in U.S. Pat. No. 4,892,729 (hereby incorporated by reference in its entirety), to overcome the above-described drawbacks of soap-based formulations. By non-lathering, we mean shaving preparations that do not contain surfactants of the lathering or foaming type, as understood by one of ordinary skill in the art.
Soap-free, non-lathering shaving preparations have found popular application as shaving lotions for use in the shower. Unfortunately, currently available shaving lotions are easily rinsed from the surface of the skin. This can make shaving of body parts difficult, if not impossible, in the shower.
Our invention is directed to improving the skin adhering ability of soap-free, non-lathering shaving preparations. We have found that adding certain ethoxylated fatty esters to a behenylquaternary surfactant-based composition produces a shave lotion that exhibits superior increased surface adherence when applied to the skin. As used herein, "surface adherence" refers to the ability of a substance to adhere to a surface and resist rinsing, and can be measured quantitatively by the amount of time it takes to rinse away completely the substance from the surface.
Ethoxylated fatty esters (otherwise known as polyether esters) have found application in cosmetic compositions as thickening agents for shampoos, conditioners, skin lotions, facial creams, and the like, as discussed in U.S. Pat. No. 5,192,462; U.S. Pat. No. 5,641,479; U.S. Pat. No. 5,610,125; U.S. Pat. No. 5,674,511; U.S. Pat. No. 5,439,682; U.S. Pat. No. 5,672,576; U.S. Pat. No. 5,575,990; and U.S. Pat. No. 5,389,305. However, none of these patents teaches or suggests the use of ethoxylated fatty esters to increase the surface adherence of a composition after application to the skin.
In short, there exists a need for a soap-free, non-lathering shaving preparation exhibiting increased surface adherence.